The Serbian winger posted a message to Benfica fans on his Facebook page on Sunday, which read: "Thank you for everything and goodbye!"

Markovic, who moved to Portugal from Partizan Belgrade in June 2013, helped Benfica to last season's Europa League final -- although he missed the defeat against Sevilla in Turin because of suspension.

He will become Liverpool's fourth summer signing, following the arrivals of England internationals Rickie Lambert and Adam Lallana from Southampton and Germany under-21 midfielder Emre Can from Bayer Leverkusen.

Meanwhile, striker Iago Aspas is set to leave Liverpool for Sevilla on a season's loan.

The 26-year-old Spanish striker is available for transfer after failing to make an impact on Merseyside following his 7.7 million pounds move from Celta Vigo in 2013.

He made just five Premier League starts last season, with his only goal for the club coming in a 2-0 FA Cup third round win over Oldham on Jan. 4.

Liverpool had considered offering Aspas in part-exchange for Sevilla left-back Alberto Moreno.

The Reds still have hopes of signing Moreno despite being unable to agree a fee with the Primera Division side -- but if the deal is to be resurrected, it will now be done separately.